The present invention relates to a novel quinolone carboxylic acid derivative and a salt thereof which exhibit excellent antimicrobial activity against both Gram positive and Gram negative microorganisms.

Quinolone carboxylic acid derivatives with diazepinyl substituents at position 7 are known from JP-A-63 132 885, JP-A-63 196 580 and J. Med.Chem Vol.33 Nr.1, 1990, p.142-146. Quinolone carboxylic acids with fluorine substituents at position 8 are known from EP-A-0 153 828. Quinolone carboxylic acids with hexahydro-1,4-oxazepin-4-yl substituents at position 7 are known from JP-A-2 115 181. Quinolone carboxylic acids with 3-oxo-1-piperazinyl substituents in position 7 are known from EP-A-0 166 939. Quinolone carboxylic acids with fluoro-methoxy substituents at position 8 are known from EP-A-0 352 123.

Synthetic antimicrobial agents such as nalidixic acid, piromidic acid, and the like are known as drugs for curing infectious diseases caused by Gram negative microorganisms. They exhibit, however, only deficient effects on intractable diseases such as pseudomoniasis and the like.

On the other hand, quinolone carboxylic acid derivatives substituted with a fluorine atom at 6 position, such as norfloxacin, ofloxacin, and cyprofloxacin, or quinolone carboxylic acid derivatives substituted with a chlorine atom at 8 position have been developed (Japanese Patent Laid-open (ko-kai) Nos. 225181/1986, 90813/1989) and clinically used because of their strong antimicrobial activity.

These conventional synthetic antimicrobial agents had defects of insufficient absorptivity in a living body, providing only low bioavailability, and of a low antimicrobial activity against Gram positive microorganisms.

Therefore, development of antimicrobial agents having strong antimicrobial activity against both Gram positive and Gram negative microorganisms, including resistant bacteria, and superior absorptivity in living bodies has been desired.

In view of such a situation, the present inventors have synthesized a number of quinolone derivatives and studied their antimicrobial activity and absorptivity in a living body, and found that quinolone carboxylic acid derivatives of the following formula (1) and their salts exhibited antimicrobial activities against Gram positive microorganisms much stronger than conventional quinolone carboxylic acid derivatives, while maintaining their strong antimicrobial activities against Gram negative microorganisms, as well as excellent absorptivity. Such findings have led to the completion of the present invention.

The present invention provides a quinolone carboxylic acid derivative having the following formula (1),
wherein Z is an oxygen atom, Y is N-R³, wherein R³ is a hydrogen atom or a C₁-C₅ alkyl group, R¹ is a hydrogen atom, an alkyl group, an aralkyl group, an ester residual group which can be hydrolyzed in living bodies, R² is a hydrogen atom or an amino group which may be substituted by one or two C₁-C₅ alkyl groups and X is a hydrogen atom or a chlorine atom; or a salt thereof;
   or wherein Z is two hydrogen atoms, Y is CH₂, SO or SO₂, R¹ is a hydrogen atom, an alkyl group, an aralkyl group, an ester residual group which can be hydrolyzed in living bodies, R² is a hydrogen atom or an amino group which may be substituted by one or two C₁-C₅ alkyl groups, X is a hydrogen atom or a chlorine atom; or a salt thereof.

The present invention also provides an antimicrobial agent comprising a quinolone carboxylic acid derivative of formula (1) or a salt thereof as an effective component.

Given as examples of groups represented by R¹ in formula (1) are, as alkyl groups, linear or branched alkyl groups having 1-12 carbon atoms, e.g., methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, n-pentyl, n-hexyl, and the like; as aralkyl groups, benzyl, phenyl ethyl, methyl benzyl, naphtyl methyl, and the like; and as ester residual groups which can be hydrolyzed in living bodies, alkanoyloxyalkyl, alkoxycarbonyloxyalkyl, carbamoylalkyl, alkoxyalkyl, and the like; specifically, acetoxymethyl, 1-acetoxyethyl, ethoxycarbonyloxymethyl, carbamoylmethyl, carbamoylethyl, methoxymethyl, methoxyethyl, and the like. Examples of amino groups which may be substituted by one or two lower alkyl groups, represented by R², include amino, methylamino, ethylamino, isopropylamino, dimethylamino, diethylamino, diisopropylamino, and the like. Examples given of halogen atoms represented by X are chlorine, fluorine, bromine, iodine. Lower alkyl groups used in the present invention may be linear or branched alkyl groups having 1-5 carbon atoms, e.g., methyl, ethyl, i-propyl, sec-butyl, t-butyl, amyl, and the like.

When R² in formula (1) is other than hydrogen, the carbon atom to which R² is bonded is asymmetrical, so that there are optical isomers; R and S compounds, for compounds (1) of the present invention. The present invention includes both the optical isomers and the racemate.

As examples of the salts of the compounds of formula (1) of the present invention, salts of alkali metal, inorganic acid, organic acid, and the like are given, and more specifically, lithium salts, sodium salts, potassium salts, and the like, as salts of alkali metal; hydrochloride, sulfate, nitrate, hydrobromide, phosphate, and the like, as salts of inorganic acids; and acetate, fumarate, maleate, lactate, citrate, tartarate, malate, oxalate, methanesulfonate, benzenesulfonate, p-toluenesulfonate, and the like, as salts of organic acid.

In the preparation of the compound of formula (1) of the present invention [Compounds (1a) and (1b)] Compound (2) and Compound (3), for example, are reacted according to the following reaction scheme to produce Compound (1a), and Compound (1a) is halogenated to produce Compound (1b).
wherein X' is a halogen atom, and R¹, R², Y and Z are the same as those previously defined.

The raw material, Compound (2), is a known compound and can be prepared by the method described, for example, in Journal of Medicinal Chemistry, 31, 983 (1989). Compound (3) is also a known compound and can be prepared by the method described, for example, in Journal of American Chemical Society, 106, 630 (1984).

In order to prepare Compound (1a) from Compound (2) and Compound (3), 1 mol of Compound (2) is reacted with 1-5 mols of Compound (3) in a solvent such as acetonitrile, dimethylsulfoxide, or the like at room temperature to 100°C for 1-7 days. After the reaction, precipitate is collected by filtration and washed with a suitable solvent, e.g., methanol, chloroform, ether, etc., to obtain a crude product. The crude product is purified by silica gel column chromatography or by recrystallization to obtain Compound (1a).

The preparation of Compound (1b) from Compound (1a) can be carried out by a method described, for example, in Japanese Patent Laid-open 90183/1989; that is, 1 mol of Compound (1a) is reacted with 1-10 mols of a halogenizing agent, such as sulfuryl chloride, chlorine, bromine, iodine, N-chlorosuccinic acid imide, N-bromosuccinic acid imide, or the like, in a suitable solvent, such as chloroform, dichloromethane, acetic acid, methanol, ethanol, or the like, at 0-100°C for 1-48 hours. After the reaction, water is added to collect precipitate by filtration and the precipitate is washed with water to produce a crude product. This crude product is purified by silica gel column chromatography or by the recrystallization to obtain Compound (1b).

If necessary, Compound (1) thus obtained is converted into a salt, such as a salt of alkali metal, inorganic acid, organic acid, or the like, according to a conventional method.

When Compound (1) of this invention thus prepared is used as an antimicrobial agent, it is administered orally at a dose of 200 to 800 mg per day or parenterally at a dose of 5 to 40 mg per day, depending on the weight, the age, the sex, the physical conditions, or the symptom of the patient or the manner of administration.

Compound (1) can be formed into various antimicrobial preparations, such as tablets, granules, powders, capsules, suspensions, injections, suppositories, or the like, according to conventional methods. When solid preparations are produced, compound (1) is mixed with excipients, and as required, with binders, disintegrators, lubricants, coloring agents, sweetening agents, flavoring agents, fillers, coating agents, sugar-coating agents, and the like, and formed into preparations such as tablets, granules, powders, capsules, suppositories, or the like according to known methods. When compound (1) is made into a preparation for injection, it is dissolved, suspended, or emulsified into an aqueous medium such as distilled water, or made into powder which is dissolvable when it is injected. Intravenous, intraarterial, intraportal, intraperitoneal, intramuscular, or subcutaneous injection are applicable.

The present invention is hereinafter described in more detail by way of examples and test examples, which are not intended to be limiting thereof.

0.265 g of 1-cyclopropyl-6,7-difluoro-4-oxoquinoline-3-carboxylic acid and 0.200 g of 2,3,4,5,6,7-hexahydro-1H-1,4-diazepin-5-one dissolved into 20 ml of acetonitrile and refluxed for 3 days. After cooling, the precipitate was collected by filtration, washed with chloroform, methanol, and ether in this order to obtain 0.300 g of colorless crystals of the target compound (yield: 83%).
¹H-NHR δ ppm(NaOD+D₂O): 0.76-1.48(m, 4H), 2.50-3.80(m, 9H), 7.10(d, J=7.7Hz, 1H), 7.56(d, J=14.1Hz, 1H), 8.48(s, 1H) m.p.: 300°C or above

0.84 ml of sulfuryl chloride was added dropwise to a suspension of 1.50 g of 1-cyclopropyl-6-fluoro-7-(2,3,4,5,6,7-hexahydro-1H-1,4-diazepin-5-one-1-yl)-4- oxoquinoline-3-carboxylic acid in 30 ml of chloroform, and the mixture was stirred for 12 hours at room temperature. After an addition of ice water, the precipitate was collected by filtration, washed with water, dried in air, and recrystallized in ethanol-chloroform to obtain 0.87 g pale yellow crystals of the target compound (yield: 53.0%).
¹H-NHR δ (CD₃OD+CDCl₃): 0.80-1.50(m, 4H), 2.50-3.00(m, 2H), 3.30-3.64(m, 7H), 7.52(s, 1H), 8.10(d, J=11.6Hz, 1H), 9.02(s, 1H) m.p.: 282-284°C (decomposed)

Compound Nos. 3-9 listed in Table 1 were prepared in the same manner as in Example 1. Physicochemical data of these compounds are given in Table 2.

Reactions were carried out in the same manner as in Example 2 to prepare Compound Nos. 10-16 listed in Table 3. Physicochemical data of these compounds are given in Table 4.

Antimicrobial activities against bacteria listed in Tables 5-7 were measured according to the MIC measurement method of The Japan Chemotherapeutic Association. Ofloxacin was used as a control. The results are shown in Tables 5-7.
   Medium: Mueller Hinton Medium
   Sample dilution: A 1,000 µg/ml solution in 25% dimethylsulfoxide was prepared. A series of solutions with various concentrations (100 µg/ml to 0.006 µg/ml) were prepared by successively diluting the solution with sterilized water by a factor of 1/2.
   Amount of inoculated bacteria: 10⁶/ml
   Cultivation conditions: 37°C, 48 hours
   Determination: after 24 hours

The compound (1) and its salt of this invention exhibit a superior antimicrobial activity, especially against Gram positive microorganisms, and are thus useful for the treatments and prevention of various infectious diseases in clinics.